The Mexican government has lambasted the National Security Agency’s systematic eavesdropping of its operations, as reported by Der Spiegel. The surveillance apparently included the hacking of an email account used by former Mexican President Felipe Calderón.

“This practice is unacceptable, illegitimate and against Mexican and international law,” Mexico’s foreign ministry stated, according to CNN, who further reported that the two governments will discuss the matter via diplomatic channels.

The NSA said that it would not comment on specific cases, but added that “as the President said in his speech at the U.N. General Assembly, we’ve begun to review the way that we gather intelligence.”

The information in the Der Spiegel report was based on documents leaked by former NSA contractor Edward Snowden.